Mobile communications network

ABSTRACT

A mobile communications network comprises a network manager for managing a plurality of mobile stations in the network, a first database holding subscriber information for mobile station subscribers in the network and in communication with the network manager via a signalling interface over which information is conveyed using one of a plurality of signalling protocols, at least one second database for communication with a packet data network via a packet data interface over which information is conveyed using one of a plurality of packet transmission protocols, said second database holding subscriber information for subscribers connected via said packet data network, and a protocol converter in communication with the at least one second database via a packet data interface and with the network manager via a signalling interface, and operable to convert between a signalling protocol used on the signalling interface and a packet transmission protocol used on the packet data interface.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a mobile communications network whichhas access to an external packet DATA network such as the internet.

(2) Description of Related Art

There are currently a significant number of internet protocol (IP)service providers using fixed telephone networks. It would be desirableto extend these to using mobile networks. It is in principle possible toconnect messages conveyed through a mobile communications network to theinternet or other switched packet data network (PDN) using generalpacket radio services (GPRS), a standard which is a packet data transferstandard compatible with GSM. It is supported in some GSM networksthrough the use of GPRS support nodes (GSN). However, access to theinternet or other packet data network in this way currently requiresthat a service provider provide a suitable gateway GPRS service node(GGSN) and a home location register (HLR) and subscriber database whichcommunicates with it in a manner compatible with existing GSM signallingstandards. Thus, a service provider would need to set up a home locationregister and subscriber database and gateway GPRS service node capableof utilising at least one of the appropriate signalling protocols usedin the SS7 stack specified by GSM. This requires a significantinvestment on the part of the service provider and as such constitutes adeterrent for providing more open access to the internet using themobile communication network.

U.S. Pat. No. 5,793,762 describes a system and method for providingInternet and data voice services to mobile subscribers. The systemincludes a Home Location Register (HLR), which is operative to store andprovide subscription data and keep track of where at least one mobileterminal is registered in order to deliver calls thereto.

WO 98/27698 describes an arrangement for establishing a packet switchedand a circuit switched connection between a first telecommunicationssystem (NSS) and a second telecommunications system (WAN) comprising: apacket switched converter (PSDC), a circuit switched converter (CSDC)and a common data communications controller (CDCC) for establishing aconnection between the converters (PSDC, CSDC).

EP 0 766 490 relates to an integrated data transfer system, theextensive basis of which is constituted by a general cellular radiosystem, and in which a radio local area network is used forcommunicating between data terminals in small areas with densecommunications. In addition, the Internet is used for fast datatransfer. The connection between networks is handled by a gatewaycomputer, which in view of the cellular radio system operates like aBase Station Controller (BSC).

BRIEF SUMMARY OF THE INVENTION

According to the present invention there is provided a mobilecommunications network comprising: a network manager (MSC) for managinga plurality of mobile stations in the network; a first database (HLR)holding subscriber information for mobile station subscribers in thenetwork and in communication with the network manager via a signallinginterface over which information is conveyed using one of a plurality ofsignalling protocols; at least one second database (LHLR) forcommunication with a packet data network via a packet data interfaceover which information is conveyed using one of a plurality of packettransmission protocols, said second database holding subscriberinformation for subscribers connected via said packet data network; anda protocol converter in communication with the at least one seconddatabase via a packet data interface and with the network manager via asignalling interface, and operable to convert between a signallingprotocol used on the signalling interface and a packet transmissionprotocol used on the packet data interface.

The first database can be a home location register as used in the GSMstandard to hold subscriber information. The at least one seconddatabase can constitute a supplementary home location register forholding subscriber information relating to users connected via thepacket data network. It is referred to herein as a “little HLR”. Morethan one of these “little HLRs” may be provided in a network. It can beimplemented using software operating on commercial UNIX or NT serversfor example, which is a much cheaper investment for new serviceproviders than the investment in the more complex signalling protocolscurrently used in GSM. The provision of a separate, second database alsoprovides a service provider with more control for managing hissubscribers and services.

Thus, the service provider need provide only the second database, and,optionally a gateway for access to other supplementary services outsidethe mobile communications network connected to the second database via apacket data interface. The service provider can then be connected to themobile networks through a roaming broker which provides the protocolconverter in the form of an interworking unit.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show how thesame may be carried into effect reference will now be made by way ofexample to the accompanying drawings in which:

FIG. 1 is a schematic diagram of relevant components of the logicalarchitecture of a mobile network;

FIG. 2 is a diagram of a signalling protocol stack;

FIG. 2 a is a diagram illustrating use of a protocol stack;

FIG. 3 is a diagram of a data transmission protocol stack;

FIG. 4 illustrates modified components of a logical architecture for thenetwork according to one embodiment of the invention;

FIG. 5 is a diagram illustrating operation of an interworking unit; and

FIG. 6 is a diagram illustrating one application of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates relevant components of a logical architecture forsupporting a mobile communications network, in this case the standardset down for a global system for mobile communications, referred toherein as GSM. In addition to providing services for mobile phones, theGSM network is extended to provide other services, referred to herein asgeneral packet radio services (GPRS). The logical architecture comprisesa base station system 2 which incorporates base transceiver stations(BTS) and base station controllers (BSC) for controlling the basetransceiver stations. The base transceiver stations themselves receiveRF signals 4 from mobile stations 6. The base station system 2 isconnected to a network manager in the form of a mobile switching centre(MSC) 8 which controls the operations of the mobile communicationnetwork. The mobile switching centre 8 is associated with a visitorlocation register (VLR) which is a database containing information aboutmobile subscribers that visit the area governed by the mobile switchingcentre 8. The mobile switching centre 8 communicates with the basestation system 2 via an A interface 10. The mobile switching centre 8and its visitor location register are also in communication with a homelocation register (HLR) 12 via a D interface 14. The home locationregister is a database that contains all the subscriber specificinformation of subscribers in the home public land mobile network(PLMN). The network provides support for GPRS services by incorporatinga gateway GPRS support node 16 and a serving GPRS support node 18. Thegateway GPRS support node 16 communicates with the home locationregister 12 via a G_(c) interface 20. The serving GPRS support node 18communicates with the home location register 12 via a G_(r) interface22. The gateway GPRS support node 16 communicates with the serving GPRSsupport node 18 via a G_(n) interface 24. The logical architecturecomponents 2, 8, 12, 16 and 18 which have just been discussed can beconsidered to form part of a first public land mobile network PLMN1. Theserving GPRS support node allows connection via a G_(p) interface 26 toa second public land mobile network PLMN2. The gateway GPRS support node16 additionally allows access to a packet data network (PDN) 28 via aG_(i) interface 30.

It will readily be appreciated that the physical implementation of thelogical architecture components and the interfaces between themsignificantly affect how information can be transferred between thecomponents. Data transfer protocols which are suited to one medium maynot transfer easily to other mediums. In order to transfer informationthrough the network as sufficiently and reliably as possible, a numberof protocols are used across each interface according to a so-calledprotocol stack. Such a protocol stack is used for example to conveyinformation between the mobile switching centre 8 and home locationregister 12 via the D interface 14. This stack is illustrated in FIG. 2and is referred to as the SS7 stack according to the GSM standard. Theprotocol stack of FIG. 2 includes a number of protocol layers asfollows.

A mobile application part (MAP) layer is an application which generatesa protocol to update location registers such as the visitor locationregister (VLR) and the home location register (HLR) 12.

A transaction capabilities application part (TCAP) is a simple protocolthat provides features for establishing a signalling dialogue betweennodes when no speech path is required.

A signalling connection control part (SCCP) provides enhanced addressingand translation features that allow the transfer of signalling messagesbetween two indirectly connected nodes when no speech connection isrequired.

The message transfer parts (MTP2, MTP3) provide reliable messagetransfer between nodes in the network.

A first protocol layer L1, provides the basic signalling protocol for RFmessages.

The use of a protocol stack is known in the art but is briefly describedherein with reference to FIG. 2 a. In FIG. 2 a, each block PL denotes aprotocol layer of the stack of FIG. 2. For the sake of simplification,the message transfer parts MTP1, MTP2 have been combined in a singleblock and denoted only MTP. A first protocol stack has layers denotedwith the suffix 1, and a second protocol stack has layers denoted withthe suffix 2. Consider the example of a message issued by the mobileswitching centre MSC 8 according to the MAP protocol, for example forupdating a register in the home location register 12. Consider that thefirst protocol stack belongs to the visitor location register VLR andthe second protocol stack belongs to the home location register HLR.Depending on the nature of the D interface 14, the message can beconveyed using one or more of the protocol layers of a protocol stack.Consider that all of the protocol layers of the stack are needed. Themessage will be conveyed from the MAP1 layer to the TCAP1 layer viaprotocol conversion and checking units 40. These units 40 add thenecessary information to the message to change the protocol, and checksfor any errors. A similar unit (of course adapted to each protocol),lies between each of the protocol layer blocks. If all of the layers ofthe protocol stack are used, the message will finally be renderedaccording to the L1 protocol and will be transferred using that protocolto the L12 protocol layer of the home location register. The protocolwill then be altered, in reverse, through the protocol layers up to theMAP2 layer. It is not necessary to use all the protocol layers in astack. It is quite feasible to consider, for example, a message conveyedbetween the MAP1 and MAP2 protocol layers, or indeed between any pair ofprotocol layers in the stacks.

It is not practical however to include in one protocol stack all of thepossible protocols that may be required in a mobile communicationnetwork and to support a large number of ancillary services such asGPRS, PDN etc. Therefore, different interfaces provide differentprotocols. FIG. 3 illustrates the protocol stack used to conveyinformation between the gateway GPRS support node 16 and the servingGPRS support node 18 via the G_(n) interface 24. This stack includesfirst and second message transfer layer protocols L1, L2, an internetprotocol layer IP, a user datagram protocol UDP and a GPRS tunnellingprotocol GTP. These protocols are used however in the same way asdescribed above with reference to FIG. 2 a.

It will be appreciated that if it is necessary, for example, to convey amessage between the HLR 12 and the PDN 28 a number of steps arerequired. The message is sent across the G_(c) interface 20 from thehome location register 12 using the SS7 signalling stack of FIG. 2 tothe gateway GPRS support node 16. From there, it is transmitted via theG_(i) interface 30 using the data transmission protocol stack accordingto FIG. 3. Thus, some conversion is necessary. This is carried out by aninterworking unit 32 which receives a message conveyed by the G_(c)interface 20 according to a first protocol of the SS7 stack and convertsthat protocol into one of the protocols of the stack of FIG. 3.

After that, the protocol layers of the data transmission stack of FIG. 3can be used as normal on the G_(i) interface 30, and also the G_(n)interface 24.

Information about subscribers to services accessible by the GGSN 16 andGSSN 18 is held in the home location register 12. Thus, with thearchitecture of FIG. 1, a service provider wishing to use the facilitiesof a mobile communication network needs to provide not only a suitablegateway node with a data transmission protocol, but also, a homelocation register for managing those services. For these purposes, he isrequired to implement the SS7 stack of FIG. 2. This is expensive and candeter potential new service providers.

The logical architecture of FIG. 4 overcomes this problem. In FIG. 4,like numerals denote like parts as in FIG. 1 and parts which have notbeen modified are omitted from FIG. 4 entirely for the sake of clarity.Thus, in respects other than those illustrated in FIG. 4, the logicalarchitecture is the same as FIG. 1.

In addition to the architectural components illustrated in FIG. 1, thereis a so-called little home location register (LHLR) 42. This is providedto manage subscriber services which are accessed through the packet datanetwork PDN 28 via gateway GPRS support node 16, or directly via theinterface 51. The little home location register 42 communicates with thegateway GPRS support node 16 via a G_(c)′ interface 44. It communicateswith the serving GPRS support node 18 via a G_(r)′ interface 46. Theseinterfaces use the data transmission stack of FIG. 3 instead of the SS7stack used on the equivalent interfaces G_(c), G_(r) in FIG. 1. Aninterworking unit 48 is provided which communicates with the little homelocation register 42 via a D′ interface 50. The D′ interface also usesthe protocol stack of FIG. 3. The interworking unit 48 provides afacility to convert between any of the protocols in the protocol stackof FIG. 3 to any of the protocols in the SS7 stack of FIG. 2 to allowcommunication if necessary with the mobile switching centre 8 and itsvisitor location register. This is illustrated in FIG. 5.

The provision of a little home location register 42 which cancommunicate using protocols more suited to data packet transmissionallows a number of different facilities to be provided as illustratedfor example in FIG. 6.

FIG. 6 illustrates a service provider SP which provides a little homelocation register 42 and a gateway GPRS support node 16 connected to oneanother via an intranet connection 44. The protocol stack of FIG. 3 canbe used to transmit data between the little home location register 42and the GGSN 16 via the intranet 44. In fact, the intranet provides theG_(c)′ interface. The little home location register 42 is connected tothe public internet 54 via the interface 60 on which transmission isexecuted using the internet protocol IP. It also has another interface60′ which likewise uses the internet protocol IP to an internet formingpart of the GPRS services. This is also connected to the GGSN 16 via aninterface 56 which uses the GPRS tunnelling protocol GTP.

A roaming broker 58 connects the GTP/internet services to the PLMN andprovides the interworking unit (IWU) 48 for the necessary protocolconversions for messages from the PLMN to the little home locationregister 42.

Thus, a subscriber can be connected to the PLMN through the publicinternet 54 and little home location register 42. The connection can beentirely on the internet using the IP interfaces 60, 60′ or through theintranet 44 and GTP interface 56.

More than one little home location register may be provided in a networkhaving one home location register HLR and one interworking unit IWU.

1. A mobile communications network comprising: a network manager (8) formanaging a plurality of mobile stations (6) in the network; a firstdatabase (12) holding subscriber information for mobile stationsubscribers in the network and in communication with the network manager(8) via a signalling interface (14) over which information is conveyedusing one of a plurality of signalling protocols; a gateway node (16) incommunication with a packet data network for supporting general packetradio services; characterised in that said communications networkcomprising: at least one second database (42) in communication with thepacket data network over a first packet data interface (51) and withsaid gateway node over a second packet data interface (44) such thatinformation is conveyed over said first and second packet datainterfaces using one of a plurality of packet transmission protocols,said second database holding subscriber information for subscribersconnected via said packet data network; a protocol converter (48) incommunication with the at least one second database (42) via a thirdpacket data interface (50) and with the network manager (8) via asignalling interface, and operable to convert between a signallingprotocol used on the signalling interface and a packet transmissionprotocol used on the packet data interface; and wherein said first (51),second (44) and third (50) packet data interfaces use the sametransmission protocol.
 2. A network according to claim 1, wherein theplurality of signalling protocols are arranged in a signalling protocolstack.
 3. A network according to claim 2, wherein the signallingprotocol stack is the SS7 stack specified according to the GSM standard.4. A network according to claim 1, wherein the plurality of packettransmission protocols are arranged in a packet transmission protocolstack.
 5. A network according to claim 4, wherein the packet datanetwork (28) is the internet (54) and one of said packet transmissionprotocols is an internet protocol (60, 60′) for transmitting informationover the internet.
 6. A network according to claim 1, wherein saidgateway node (16) is used for access to supplementary services outsidethe mobile communications network.
 7. A network according to claim 1,wherein the first database (12) is a home location register according tothe GSM standard.
 8. A network according to claim 1, wherein the networkmanager (8) includes a visitor location register for holding informationabout mobile station subscribers visiting the network.